Measurement Computing Data Acquisition Systems rev.10.4 - Manual (Page 360)

G-2 Glossary
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Programmer’s Manual
Array
A collection of quantities [of the same data type] that are located in contiguous memory.
Asynchronous
Describes an event or action that is not temporally related to other events or actions. Normally, this describes an
event or action that uses no synchronization method (such as an external or internal clock) to coordinate the event or
action with other events or actions.
BCD (Binary Coded Decimal)
Refers to a data format where each byte represents a digit from 0 to 9. This is used mostly in reference to the
counter mode selection for the 9513 chip. If used, 4 bytes are available, each byte representing a digit between 0
and 9 multiplied by subsequent powers of 10, from 0 to 3. Thus, the range for this number would be from 0 to 9,999
(dec).
Bit Mask
A collection of bits (usually 8 to 32-bits long) that is used to configure devices, channels or operations. A bit mask
can also represents the state of certain operations, and events detected by the device. In a bit mask, each bit has
special meaning that can be interpreted using the bit mask enumerations located in each specific programming
language’s API header files.
BOOL
A 32-bit Boolean (4 bytes) quantity that can take on either true (
≠ 0) or false (= 0) values. This parameter type
should be passed by value according to the dictates of the programming language used.
Boolean
A value that indicates a binary state of either true (see true) or false (see false).
Buffer (circular)
A buffer that will continue the reading or writing operation upon reaching the end of the buffer by starting again at
the beginning of the buffer. This style of buffer is normally useful when there is not enough memory available to
hold the entire acquisition input or waveform/pattern output data.
Buffer (linear)
A buffer that will terminate the reading or writing operation upon reaching the end of the buffer. Once the end of
the buffer has been reached, no more data may be read from or written to the buffer. This style of buffer is normally
useful when there is enough memory available to hold the entire acquisition input or waveform/pattern output data.
Buffer Position
The current position of the read or write operation of the buffer. If the buffer is being used to hold acquisition input
data, then this position refers to the write (or head) position within the buffer at which the driver will store the next
available data block. If the buffer is being used to buffer waveform/pattern output data, then this position refers to
the read (or tail) position within the buffer from which the driver will retrieve the next available data block.
Channel
In reference to Daq products, a channel refers to a single input, or output entity. In a broader sense, an input channel
is a signal path between the transducer at the point of measurement and the data acquisition system. A channel can
go through various stages (buffers, multiplexers, or signal conditioning amplifiers and filters). Input channels are
periodically sampled for readings. An output channel from a device can be digital or analog. Outputs can vary (as
dictated by a program) in response to an input channel signal.
Channel Scan Configuration
See Channel Scan Group.
Channel Scan Group
A list of input channel configurations that fully define each individual channel’s configuration for a particular data
acquisition operation.